Add active, link, visited, negative, neutral and positive background colors

Summary: These colors were added to Kirigami and qqc2-desktop-style, so I had to add them here too.

Reviewers: #kirigami, #plasma, mart

Reviewed By: #kirigami, #plasma, mart

Subscribers: plasma-devel

Tags: #plasma, #kirigami

Differential Revision: https://phabricator.kde.org/D26746